Constant tension unwinding mechanism



Nov. 11, 1958 R. LE B. BOWEN, JR 2,859,921

CONSTANT TENSION UNWINDING MECHANISM Original Filed March 25, 1953INVENTOR. RICHARD LEBARON BOWEN,JR.

AT TORNEYS United States Patent 2,859,921 CONSTANT TENSION UNWINDINGMECHANISM Richard Le Baron Bowen, Jr., Barrington, R. I.

Original application March 25, 1953, Serial No. 344,520, now Patent No.2,781,178, dated February 12, 1957. Divided and this applicationNovember 16, 1956, Serial No. 622,653

2 Claims. (Cl. 242-75.45)

This invention relates to a constant web tension unwinding mechanism andmore particularly to a mechanism for maintaining a constant speed on theweb tensioning mechanism through a variable speed transmissionresponsive to the change in roll diameter which reacts to control thespeed of the braking mechanism.

One of the objects of the present invention is to provide a constantbraking force in a web unwinding mechanism.

Another object of the present invention is to provide a constant tensionunwinding mechanism which will operate automatically without anyattention from an operator.

Still another object is the provision of a constant tension unwindingmechanism which will inherently permit the accurate duplication of thebraking force.

Other objects of the present invention will be pointed out in part andbecome apparent in part in the following specification and claims.

The present application is a divisional application of my co-pendingapplication Serial No. 344,520 now Patent No. 2,781,178 dated February12, 1957.

Uniform or constant tension is a prerequisite to uniformity of productin many web processing machines such as textiles, paper, imitationleather, printing and the like. Especially is this true in a web coatingmachine where the tension in the web efiect's the nature and thick nessof the coating material being applied to the web. Thus, when a supplyroll of cloth is placed in a machine, the cloth should be drawn off at aconstant speed and at a given tension.

It is common practice to put a mechanical brake on the shaft of theunwinding roll of material. As the diameter of the roll decreases, thespeed or linear travel of the cloth or web is maintained constant, butthe speed of the unwinding roll shaft increases in proportion to thedecreasing diameter of the roll. If the setting of the mechanical brakeis left constant, the tension produced on the web continues to increasein proportion to the increasing speed of the unwinding roll shaft. Insuch a set up it is necessary to decrease the drag or setting of themechanical brake on the roll shaft if the tension is to be maintainedconstant. Past devices have failed to automatically control the drag andthereby regulate the tension accurately in accordance with the changingtension produced as the supply roll decreases in diameter.

This failure was due in part to the nature of the braking mechanismwhich consisted of the conventional mechanical arrangement of a brakedrum and a shoe provided with a brake lining. The coefficient offriction between the drum and shoe varied due to the heating caused bythe period of operation and the unevenness of the parts and oil and dustaccumulation so that the brake slipped and grabbed. There was no way ofdetermining a brake setting for future use since the brake liningcontinually wore down. The present invention contemplates an oil pump asa brake, the pressure of which is always determinable for future precisesettings.

In the drawings:

The single figure is a diagrammatic view of the present invention.

Referring to the drawing, a strip of web material 11 is being withdrawnfrom a beam 12 by means of a drum 16. Beam 12 is secured to an axle 13which has fixed to it bevel gear 14 which meshes with bevel gear 15fixed to shaft 20 of a continuously variable speed transmission,generally indicated by reference character 17. A second shaft ofvariable speed transmission 17 is operatively connected to a gearpumpgenerally indicated by reference character 35 through a shaft 36,sprocket 33 fixed to shaft 36, sprocket 32 fixed to shaft 21 and chain34 connecting sprockets 32, 33.

A reservoir 38 is provided and is operatively connected to gear pump 35through suction line 37 and discharge line 40. A discharge valve 41inserted in line 40 controls the power exerted by the gear pump 35. Apressure gage 42 inserted in line 40 gives a relative indication of thispower.

The variable speed transmission 17 comprises a pair of parallel shafts20 and 21 rotatably mounted in a housing 22. Each shaft 20, 21 carries apair of coned disks 23, 24, respectively, forming expansive V pulleyswhich are splined to said shafts. Coned disks 23, 24 are operativelyconnected through edge-active belt 25 and may be simultaneously andoppositely adjusted to provide variable speed by the simultaneousadjustment of levers 26, 27 which are operatively connected to coneddisks 23, 24 and pivotally separated by lever 28.

Means for the movement of levers 26, 27 is provided as follows: A bellcrank arm is pivotally mounted at 101 to a bracket 102 secured tohousing 22 and having a follower roller 103 rotatably mounted at 104which bears against the outside diameter of beam 12 to sense thedecrease in the size of beam 12. A link 105 is pivotally mounted to bellcrank arm 100 at 106 and to lever 27 at 107. A link 108 pivotallymounted to bell crank arm 100 at 110 connects to lever 26 at 111. Aspring 112 is connected to bell crank lever 100 at 113 and to housing 22at 114. The spring causes the follower roller to ride against the beam12.

In operation it is self-evident that as the diameter of the beam 12decreases, bell crank lever 100 will move levers 26 and 27 thus changingthe speed of the transmission 17. This movement will maintain the speedof shaft 21 essentially constant. Since the speed of shaft 21 ismaintained constant, the power applied by pump 35 will likewise remainconstant, thereby applying constant tension to the web 11.

I claim:

1. In a constant tension unwinding mechanism, a beam carrying a web,said web travelling at a constant linear speed, a variable speedtransmission provided with a first shaft, a second shaft, and a speedchanging mechanism, said first shaft being arranged for drivingengagement with said beam, a hydraulic circuit including a gear pump anda throttling restriction, said second shaft being arranged for directdriving engagement with said gear pump,

Patented Nov. 11, 1958 a follower roller engaging said beam, and meansconnecting said speed changing mechanism with said follower roller.

2. In a constant tension unwinding mechanism, a beam carrying a web,said web travelling at a constant linear speed, a variable speedtransmission provided with a first shaft, a second shaft, and a speedchanging mechanism, said first shaft being arranged for drivingengagement with said beam, a gear pump and a fluid reservoir therefor, asuction and discharge line for said gear pump connected to said,reservoir, a throttling valve in said discharge. line,"

a driving connection between said gear pump and said second shaft, abell crank arm with a follower roller adapted to engage the periphery ofsaid beam, means for urging said roller towards said beam, and means forconnecting said bell crank to said speed changing mechanism.

References Cited in the file of this patent UNITED STATES PATENTS

